1. Field of the Invention
The present invention is an improved contactor with improved electrode for diagnostic purposes, designed for establishing electric communication between organic tissue, such as the skin of a human or animal body, and circuitry of associated monitoring or testing instrument.
2. Brief Description of Prior Art
Prior art contactors related to the present invention are described in U.S. Pat. No. 3,640,270 issued Feb. 8, 1972 and U.S. Pat. No. 4,556,065 issued Dec. 3, 1985. Both patents name Heiner Hoffmann as the inventor. As disclosed in these prior patents, the typical prior art contactor of similar operation to the contactor of the present invention has a generally cup-shaped housing of non-metallic material with a mouth bounded by a tissue engaging rim; the housing contains an electrode which is recessed within the rim but accessible by way of its mouth so as to be able to make contact with the skin of a human or animal to be tested. The mouth of the cup communicates with a low air pressure zone or vacuum inside a conduit which is traversed by a flow of high-pressure gas, generally air, and is embedded in the elastomeric material of the housing. The low-pressure zone in the recess of the housing is used to secure the contactor against organic tissue. The venturi metal tube also forms part of a conductive connection between the external conduit and the electrode. The contact electrode of U.S. Pat. No. 4,556,065 use a relatively expensive plate of coherent particles-sintered or simply pressed of a mixture of silver and one or more silver salts such as silver chloride, silver bromide, silver rhodanide or silver cyanide. Such an electrode, which has low electrical contact resistance, must be protected from interaction with adjoining elements of different metallic materials which can give rise to detrimental local currents. It is for this reason, as described in the U.S. patents referred to above, a contact plate consisting of afore described compacted mixture of a metallic silver and a silver salt is supported on a metallic body coated with silver at least in its area adjoining the plate. U.S. Pat. No. 4,556,065 also shows a retaining screw which holds the contact plate onto the supporting body and consists at least on an outer surface of nonconductive material; a titanium screw, with an oxide layer on its surface. An electrode of this prior art type, comprising a massive metallic supporting body made at least partly of silver, is very expensive compared to the electrode of the present invention. Reference may also be made to prior art U.S. Pat. No. 4,248,243, showing a contactor connected to a diagnostic apparatus such as an electrocardiograph.
Disclosed is an improved contactor and electrode for establishing electrically conductive communication with organic tissue, the contactor including a cup-shaped housing of one-piece rubbery material, the material impervious to air passage, the housing including a closing end-wall connected across an annular sidewall. The sidewall has a free terminal edge defining a rim which defines or bounds an open mouth into a main recess of the housing. The electrode or improved electrode for contacting organic tissue is positioned in the recess. The electrode comprises a contact plate with first side facing the housing mouth, and a second side with a pair of leg-like extensions and a limiter post centered between the legs, the legs and limiter post coextensive away from the back side of the contact plate. The electrode is an inexpensive and lightweight one-piece molded plastics base or substrate which is coated with a thin and thus inexpensive exterior layer of silver/silver chloride so as to be electrically conductive on the exterior surface of the electrode. A coating of low resistance electrically conductive material such as a silver based material other than silver/silver chloride could be used on the exterior of the electrode, although we prefer silver/silver chloride. The leg extensions of the electrode are resilient and spaced apart for receiving a venturi tube snapped or clamped against by the legs to physically and electrically connect with a venturi tube. The venturi tube is mounted extending through the housing. The venturi tube is electrically conductive at least on the exterior surface thereof, and preferably is gold plated so corrosion will not occur and the high electrical conductivity will remain over a long period of time, although some other highly conductive non-corroding material might be used instead of the gold. The inexpensive electrode can be readily replaced, if ever needed due to wear with only the human hand (no tools). The electrode snaps in and out of place relative to the venturi and housing by hand. The electrode, venturi tube and housing are quite durable and can be chemically cleaned or sanitized, therefore our contactor is very inexpensive to use, such as in a hospital setting for a long period of time, such as years for example.
The venturi tube has a suction port positioned such that when high pressure gas (gas can herein be the same as air) is passed through the venturi tube, a low pressure or vacuum is created within the recess of the housing. Such vacuum in the recess is capable of allowing tissue, the tissue sealingly engaging the housing rim, and the housing to move toward one another to bring the tissue into contact with the electrode plate to establish electrical conductive contact with the tissue. The vacuum also holds the contactor stationary against the tissue regardless of orientation of the contactor, with this good holding power (improved over the prior art) aided by the fact the contactor is light in weight. The venturi tube is electrically conductive from the electrode legs to a threaded end of the tube, the threaded end is exposed for connection to a pressurized gas line which also includes an electrical conductor leading back to the testing instrument. The conductor of the gas line is connected to a conductive threaded end of the gas line which connects to the venturi tube, and the other end of the gas line conductor connects to or is part of a circuit of an associated testing or monitoring instrument. Whereby the patient tissue is electrically connected through the electrode plate to the electrode legs to the venturi tube to the threaded ends (or equivalent connectable ends) of the tube and gas supply line and the supply line output conductor (wire) to the associated testing or monitoring instrument such as an electrocardiograph for example.
The general object of our present invention is to provide an improved electrode structure useful for defining an improved contactor, and which is far less expensive, lighter in weight and thus more stable on tissue at a given vacuum, highly sensitive, and safer than those of the prior art, and capable of being disassembled and assembled such as for cleaning in a hospital setting without requiring tools beyond the human hands. Our contactor also retains and enhances the advantages of low contact resistance and avoidance of local voltage differences which can give rise to destructive currents. Another object is to provide structuring in the contactor for conveniently connecting our improved electrode to an external circuit of an associated instrument with the aid of a metallic venturi tube.
Our novel contactor with novel electrode is inexpensive to produce, provides improved functionality compared to the related prior art, and thus advances the art.
These, as well as other objects and advantages will become increasingly appreciated with continued reading and with an examination of the attached drawings.